Sound generating means



July 28, 1931. c. P. MADSEN 1,816,597

SOUND GENERATING MEANS 7 Filed Dec. 50, 1925- 2 Sheets-Sheet 1 ATTORN Y July 28, 1931. c. P. MADSEN 1,816,597

SOUND GENERATING MEANS Filed Dec. 30, 1925 2 Sheets-Sheet 2 3 awvemiioz a n W M It 6 9331;; (liken wag Patented July 28, 1931 UNITED STATES PATENT OFFICE CHARLES P. MADSEN, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO WILLIAM W. VARNEY, OF BALTIMORE, MARYLAND SOUND GENERATING MEANS Application filed December 30, 1925.

My; invention relates to method and devices for translating mechanical vibrations into air waves, and one object is to provide an improved structure of the type illustrated inimy'copending application, Serial No. 27,206, in which my new method may be .used and which is .intended primarily for use in connection with phonographs, but which may also be used for electrically operated' devices, such as radio loud speakers,

etc.

In the pending application I disclosed a new method of generating air waves of sound frequency. That method consists briefly, in oscillating at its support a relatively light but rigid member, of apprec1- able area to produce a column of sustained air waves. 3 An important factor 111 that method isproviding the proper resilience at ithe properv point. In said application I disclosed that the proper point to apply the resilience is as close as possible to the ax s of. rotation of-the member supportlng in that case the bell-crank or other connecting means betweenthe groove of the record and the apex of the diaphragm.

I set forth. in the above mentioned application that any resilient means was operative, but that I preferred the use of an organic resilient material preferably initlally tensioned and then compressed. I have found that springs of the type usually used in the old art on sound boxes and which have a-volute characteristic do not produce satisfactory results, the reason being probably that' the springs are used in entirely different ways from that described herein. In the case of the sound boX,,springs are used for initially producing tension on the Serial No. 78,483.

the vibrating system produces satisfactory results.

I find that by using my method with a a spring of a new type a result equal to, and in many cases better than that produced by the resilient organic material is obtained. My new type of spring for this purpose is a torsional spring by which I mean a spring that is twisted back and forth or rotated instead of being bent or flexed is a volute. I find furthermore that it is desirable to make an integral union bet-ween the spring and its two conjugate members the relatively heavy body or reproducer head and the vibrating member, inthis case a bell crank.

In the drawings. of the herein-described embodiment of my invention Fig. l is aplan view of a portable phonograph such asis described in my previous application referred to; Fig. 2 being a side view in eleva tion of the same; Fig. 3 is a view in partial section in elevation taken through line 3-3 of Fig. 1; Fig. 4 is a view taken at right angles to that shown in Fig. 3, looking in the direction of line 4l of Fig. 1; Fig. 5 is a view taken at right angles to that shown in Fig. 3 of the same parts, being a plan View partially in section; Fig. 6 is a View similar to that shown in Fig. 3 taken on the same lines as Fig. 3 but showing a modification of my invention; Fig. 7 is another view taken similar to Fig. 3 on the same lines, but shows another modification of my invention; Fig. 8 is a plan view taken on line 88 of Fig. 7, the spring being in section and the vibrating means removed; Fig. 9 is a view similar to that shown in Fig. 3 taken on the same lines as Fig. 3 but showing another modification of my invention and the one I prefer if manufacturing conditions are adapted thereto; and Fig. 10 is a plan view of the modifications shown in Fig. 9.

Similar numerals refer to similar parts throughout the several views.

Referring to Figs. 38, 1 is the reproducer head and weight to which is secured conjugate member 2 by means of screw or fastening 3. 4 is a reproducer supporting means, or spindle, which carries rocker arm 5 which, shown, is a bell-crank; said supporting means 4 as shown in Fig. 5 is a flat spring clamped between reproducer head 1 and conjugate member 2 and is secured into rocker arm 5 so as LG form an integral structure therewith. (3 is a cone member secured to rocker arm 5 by means of stud pin 7. 8 is a conjugate cone member between wnich two cone members 6 and 8 is secured vibrating cone or oscillating mei 9 by means of stud pin 7 and knurl nut 10. 11 is the needle or stylus secured in stylus holder 12 in the usual way by means of stylus holder screw 13.

One embodiment of my invention is shown in Fig. 6, in which case the mounting blocks and screws are the same as those in the copending application above referred to, the spindle a in which case is wound with a resilient material, such as rubber. Instead, however, of winding the spindle with resilient material or organic coating, the spindle X in this case fits the reproducer head at one portion and is rigidly secured therein and is decreased in diameter near the point of movement to form a spring, as shown at 14, and further out a shoulder 15 is formed of slightly smaller diameter than the body of the spindle l; this shoulder 15 is thus free to move within the hole in the repro ducer head, and conjugate member 2, but prevents breaking of the spring portion 14 if excessively bent. In operation this neck, or spring portion 14, oscillates about its center when used on lateral cut records. This structure will also" play hill-and-dale records fairly well, but in this case the neck or spring portion 14 is flexed up and down with a volute characteristic which does not give as fine reproduction as a torsional spring in the playing of lateral cut records.

16 is a record of the ordinary type, which may be either hill-and-dale or lateral cut, and which operates the stylus 11 by means of its grooves as the same is revolved, 17 being the platen revolving the record by any well-known means, and 18 is the reproducer supporting to which is secured reproducer head and weight 1 with its conjugate member 2.

I have shown a modification of my invention in Figs. 8, 4 and 5, in which the reproducer supporting means or spindle e is a piece of flat clock spring, one end of which is united firmly inthe rocker-arm or bell-crank 5, while the other end is clamped preferably in a saw slot in the reproducer head and weight 1 by means of fastening bolt or screw 3, thus forming in substance a unit structure of the reproducer head and supporting moans. Referring to Fig. 5, the dotted indication of reproducer spindle 4: or its equival nt the flat clock spring shows the method of adjustment for obtaining correct response.

An important item in the successful or satisfactory operation of this system of sound reproducing and means for accomplishing the same is the securing the end of the supporting means 4: in the rocker-arm or bell-crank 5. I have found that no prac tical mechanical fastening means, such as threading or riveting, will withstand the vibration for any length of time without loosening. Even an electrically welded joint will cause trouble unless the entire contacting surfaces are welded. The slightest space in these joints will set up false vibrations. Soft solder has insufficient strength for the purpose and hard soldering, such as the use of silver solder, cannot be used without injuring the spring or supporting member i.

I have, however, discovered these joints can be satisfactorily and permanently united with pure metallic tin. To do this I prefer mixing the tin in finely divided form with suitable flux as zinc chloride and apply this to the joints in a paste. The whole structure is then brought to slightly above the melting point of tin in an electric furnace, but below the annealing point of the sprin Referring to Figs. 9 and 10 in which the weight or reproducer head is provided with a saw slot into which is inserted a flat clock spring 4:, 5 is the bell-crank which is slotted and into which slot is inserted the opposite end of the spring 4. Bell-crank 5 is spaced a definite distance from reproducer head 1 depending upon the size and resilience of the spring 4. This spacing for correct response is determined by trial. The whole is then put in an electric furnace, the parts previously being coated with tin dust and flux as above suggested. Reproducer head 1 may be made by die casting in which case the spring 4 is placed in the mould and cast in as a chill and then bell-crank 5 fastened on as before.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a sound generating means provided with a stylus-carrying member and a support therefor, a diaphragm wholly carried by said stylus-carrying member and an intermediate means between said stylus-carrying member and said support wholly sup porting said stylus-carrying member consisting of a spring secured to each of said two members.

2. In a phonograph provided with a reproducer head relatively stationary and a vibrating means relatively movable, a supporting means rigid in said reproducer head and rigid in said vibrating means and provided with a spring portion between said two members operating in a cavity in one of said members, and an enlarged portion on said spring portion to bear against the walls of said cavity only upon excessive relative movement of said two members.

3. In an acoustic device provided with a stylus carrying member, means for generating air Waves of sound frequency consisting of, a diaphragm, a supporting member, and a flexible supporting means between said stylus carrying member and said supporting member and rigidly secured to both wholly supporting said stylus carrying member.

4. In an acoustic device as claimed in claim 3, and in which said flexible supporting means consists of a spring, one end of which is secured to the diaphragm and the other end to the supporting member.

5. In an acoustic device provided with a stylus carrying member and a support therefor, a diaphragm wholly carried by said stylus carrying member, intermediate means between said stylus carrying member and said support for supporting said stylus carrying member, said intermediate means consisting of a member held rigidly supported at one end by said support and rigidly supported at the other end by the stylus carrying member and being of reduced flexible sectional area between its ends.

CHARLES P. MADSEN. 

